[mpich-discuss] How to find out maximum number of processes in mpiexec configuration

[Yauheni Zelenko]

Hi, Rajeev!

Thank you for suggestion!

However I grepped through MPI 1.3.1 code and see that this variable will be initialized only from command line, but not from combination of -host/host list file and -ppn (in Hydra), what may serve my purpose.

Eugene.
________________________________________
From: mpich-discuss-bounces at mcs.anl.gov [mpich-discuss-bounces at mcs.anl.gov] On Behalf Of Rajeev Thakur [thakur at mcs.anl.gov]
Sent: Wednesday, January 26, 2011 1:23 PM
To: mpich-discuss at mcs.anl.gov
Subject: Re: [mpich-discuss] How to find out maximum number of processes in     mpiexec configuration

mpiexec will let you run as many processes as many as you want -- to the extent that the OS can run that many processes.

For dynamic processes (Comm_spawn), MPI defines an attribute on MPI_COMM_WORLD called MPI_UNIVERSE_SIZE, whose value indicates how many processes can be started with Comm_spawn. See the first line on pg 308 in the MPI 2.2 standard.

Rajeev


On Jan 25, 2011, at 5:58 PM, Yauheni Zelenko wrote:

> Hi!
>
> Is there any way to find out how much MPI processes are allowed to run by current mpiexec configuration inside MPI application?
>
> I want to replicate mpiexec default behavior (when -n is not specified and processes are started on all available hosts) with MPI_Comm_spawn() when only single process starts from mpiexec (-n 1) and all other processes will be spawned from it later.
>
> Eugene.
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